Summary of Significant Accounting Policies (Schedule of Other Accruals and Current Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Sep. 30, 2025
Summary Of Significant Accounting Policies [Line Items]
Accrued Capital Expenditures	$ 47,178	$ 45,932
Regulatory Liabilities	26,367	20,624
Reserve for Gas Replacement	2,799	0
Liability for Royalty and Working Interests	36,608	28,076
Pennsylvania Impact Fee	19,955	14,923
Non-Qualified Benefit Plan Liability	11,567	11,567
Other	54,668	53,567
Other Accruals and Current Liabilities	209,202	174,689
Federal Income Taxes Payable
Summary Of Significant Accounting Policies [Line Items]
Federal Income Taxes Payable	5,384	0
State Income Taxes Payable
Summary Of Significant Accounting Policies [Line Items]
Federal Income Taxes Payable	$ 4,676	$ 0